A check valve is a type of one-way valve used in the control fluid flow through conduits. The check valve permits the flow of fluid in a first direction through a conduit and prevents fluid flow in the reverse direction. A check valve is generally constructed with a disk which is mounted to a pivoting hinge. When fluid is flowing in the allowed direction, the fluid forces the disk to pivot upward to allow passage. When there is no fluid flow or when fluid attempts to flow in the reverse direction, the disk pivots (usually gravity drop) down to seal the conduit and prevent reverse flow. Typically, all of the parts of the check valve are located inside the valve chamber with no external parts available for visual inspection.
Since it is difficult, if not impossible, to achieve visual inspection of a check valve, the dangerous reality is that a user will generally not know if the check valve is actually working until the valve is needed; at which time, it may be too late. Under most operating conditions, the check valve stays normally open on a continuous basis because pumps are in constant operation and fluid is constantly being pumped through the conduit in the allowed flow direction. Thus, it can be seen that the disk or other parts of the check valve may be broken and simply lying in the conduit and no one will know of a problem; and, when the "check" function is required, the valve can not perform. Such unfortunate events are well documented in the industry. Furthermore, it is being more and more appreciated that undersized valves, oversized valves and certain turbulent conditions in the conduit can result in harmful, damaging vibration and "bouncing" of the check valve disk. There are not practical methods in the prior art to check for the existence of these harmful vibrations. To date, the present inventors are unaware of any systems available for testing the condition of a check valve without either tearing down the valve assembly or allowing reverse fluid flow.